Investments (Credit Quality of Commercial Mortgage Loans) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans, Gross	$ 84,344	$ 80,635
Commercial Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	6,456
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	8,996
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	8,380
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	6,678
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,469
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	13,137
Financing Receivable, Revolving	2,318
Mortgage Loans, Gross	$ 52,434	$ 49,624
Loans Receivable Commercial Mortgage Percentage	100.00%
Commercial Mortgage Loans | Less than 65%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 4,960
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	4,793
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	5,620
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	4,299
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	5,103
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	9,846
Financing Receivable, Revolving	2,318
Mortgage Loans, Gross	$ 36,939
Loans Receivable Commercial Mortgage Percentage	70.40%
Commercial Mortgage Loans | 65% to 75%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 1,455
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	4,057
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	2,450
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	1,554
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	960
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,861
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 12,337
Loans Receivable Commercial Mortgage Percentage	23.50%
Commercial Mortgage Loans | 76% to 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 33
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	135
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	62
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	403
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	273
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	281
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 1,187
Loans Receivable Commercial Mortgage Percentage	2.30%
Commercial Mortgage Loans | Greater than 80%
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 8
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	11
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	248
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	422
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	133
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	1,149
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 1,971
Loans Receivable Commercial Mortgage Percentage	3.80%
Commercial Mortgage Loans | Greater than 1.20x
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 5,896
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	8,537
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	8,194
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	6,133
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	6,129
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	12,543
Financing Receivable, Revolving	2,318
Mortgage Loans, Gross	$ 49,750
Loans Receivable Commercial Mortgage Percentage	94.90%
Commercial Mortgage Loans | 1.00x - 1.20x
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 351
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	0
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	18
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	204
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	340
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	492
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 1,405
Loans Receivable Commercial Mortgage Percentage	2.70%
Commercial Mortgage Loans | Less than 1.00x
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Year One, Originated, Current Fiscal Year	$ 209
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year	459
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year	168
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year	341
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year	0
Financing Receivable, Originated, More than Five Years before Current Fiscal Year	102
Financing Receivable, Revolving	0
Mortgage Loans, Gross	$ 1,279
Loans Receivable Commercial Mortgage Percentage	2.40%